DESCRIPTION:(Applicant's Abstract) The neurotransmitter acetylcholine mediates a variety of responses within the central nervous system and plays an important role in memory function and cognition. Cholinergic cells within the basal forebrain denerate in Alzheimer's disease, a disorder associated with memory dysfunction and progressive cognitive decline. Research efforts have focused on developing selective M1 muscarinic agonists for the treatment of Alzheimer's disease. Over the past few years, several putative M1 agonists have been identified. The proposal focuses on the design, synthesis, and biological testing of novel compounds as selective muscarinic ligands. Chemical synthesis focuses on exploring a radically new approach to the development of muscarinic agonists, based on a novel series of bis-thiadiazole derivatives that display very high potency and activity at M1 receptors. Structure activity and molecular modeling studies will help identify the molecular features that contribute to activity and provide a basis for the rational design and synthesis of new ligands. In addition to pharmacological characterization of new compounds, biological studies will compare the affinity and efficiacy of several putative slective M1 muscarinic agonists at muscarinic receptors expressed in cultured cell lines and in the brain. Further studies will examine the ability of a few active and slective compounds to penetrate into the brain and reverse memory deficits associated with lesions of the septohippocampal cholinergic system. The overall goals of the project are to identify ligands with improved selectivity for muscarinic receptor subtypes, thereby providing important new pharmacological tools. A compound with high M1 agonists activity and the ability to penetrate into the brain also could become a drug candidate for the treatment of Alzheimer's disease. These studies will help determine the therapeutic utility of selective muscarinic agonists in the treatment of Alzheimer's disease. In addition the research could provide new approaches to the synthesis of compounds useful in a variety of neurological disorders.